Volcanic Emissions in the Atmosphere

Dear Colleagues,

Volcanic eruptions are usually characterized by the emissions of tephra particles (i.e., all kind of particles injected into the atmosphere regardless of their size, shape and composition), as well as a variety of trace gases. Volcanic ash (i.e., tephra particles less than 2 mm in size) is transported from its source through a buoyant plume that progressively spreads out to form an ash cloud, from which ash falls, and is dispersed by atmospheric processes to form deposits on the ground. Volcanic plumes and clouds are complex multi-phase environments of which the spatial and temporal evolutions are highly worth investigating for two main reasons: i) to prevent disruption to human activities and the surrounding environment, including the collapse of buildings, lifelines, and transport networks (e.g., hazards for aviation); and ii) provide an opportunity to investigate subsurface volcanic processes.

The prompt detection of explosive volcanic eruptions and the determination of eruption–column altitude and ash–cloud movement are critical factors in the mitigation of volcanic risks. Volcanic ash transport and dispersal (VATD) models can be used to mitigate the hazards posed by volcanic tephra, but their practical use requires an accurate estimate of eruption source parameters, namely the eruption plume dynamics and tephra granulometry. Nowadays, VATD models are often run using incomplete data of total grain size spectra and mass eruption rate and few studies have tried to fill this gap.

In general, retrieval of near-source parameters during the eruption phase is not an easy task because of the difficulties in direct measurements and the intrinsic space–time variability. For this purpose, several remote sensing observations are exploited. These include those based on i) the thermal infrared channels available on both Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) satellites used to estimate the dispersal fine-ash cloud up to synoptic scales; ii) microwave (MW) channels, available on LEO satellites, occasionally used to carry additional information on the columnar content near the volcano source due to their lower opacity; iii) ground-based weather and non-weather radars used to provide a more complete view in terms of spatial and temporal sampling and estimate of source parameters in all weather conditions; iv) infrasonic arrays for eruption onset detection; v) LiDAR for fine-ash particle retrievals and cloud thickness; vi) thermal and visible cameras for plume dynamical imaging, as well as in situ measurements, such those from vii) ash collectors and size samplers (also used to characterize and assess remote sensing retrievals).

Although a convincing strategy for the full integration of the aforementioned tools into an early warning system is still lacking, many efforts are being made by the research community in this direction. The overarching goal of this Special Issue is to invite contributions from experts in the various disciplines involved in the definition of volcanic emissions in the atmosphere and source parameters. In particular, the Special Issue is focused on:

• Satellite remote sensing tools for the detection, monitoring and quantification of volcanic emissions (e.g. sensors working in the visible, ultraviolet, infrared, and/or microwave band).
• Ground based remote sensing for source parameters definition (e.g., radars, LiDAR, cameras, infrasounds, in situ sampling of granulometry, new instruments, etc.).
• Volcanic ash transport and dispersal
• Integrated warning systems for operational purposes.

In addition, this Special Issue will be the perfect place to bring together different communities working on volcanic emissions, including volcanologists, meteorologists, remote sensing experts, and model developers/users.

Dr. Mario Montopoli
Guest Editor

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• satellite and ground based remote sensing of volcanic clouds
• volcanic ash transport and dispersal model
• volcanic emission integrated warning systems for operational purposes